IntensiveLine.shader

Shader "Custom/IntensiveLine"
{
	Properties
	{
		_LineWidth("LineWidth", Range(0,1)) = 0.5
		_CenterRadius("CenterRadius", Range(0,1)) = 0.5
	}

	SubShader
	{
		// No culling or depth
		// Cull Off ZWrite Off ZTest Always

		Pass
		{
			CGPROGRAM
// Upgrade NOTE: excluded shader from DX11, Xbox360, OpenGL ES 2.0 because it uses unsized arrays
#pragma exclude_renderers d3d11 xbox360 gles

			#pragma vertex vert
			#pragma fragment frag
			#pragma target 3.0

			#include "UnityCG.cginc"

			uniform float _CenterRadius;
			uniform float _LineWidth;

			struct appdata
			{
				float4 vertex   : POSITION;
				float3 normal   : NORMAL;
				float4 texcoord : TEXCOORD0;
			};

			float4 vert (appdata v) : POSITION
			{
			    return mul (UNITY_MATRIX_MVP, v.vertex);
			}

			float which_side(float2 p1, float2 p2, float2 p3) {
				float result = p1.x * (p2.y - p3.y) + p2.x * (p3.y - p1.y) + p3.x * (p1.y - p2.y);
                return result;
			}

			bool in_triangle(float2 xy, float2 pa, float2 pb, float2 pc) {
				float pab = which_side(xy, pa, pb);
				float pbc = which_side(xy, pb, pc);
				float pca = which_side(xy, pc, pa);

				if (0 < pab && 0 < pbc && 0 < pca) {
					return true;
				}
				else if (0 > pab && 0 > pbc && 0 > pca) {
					return true;
				}

				return false;
			}

			bool in_triangle_line(float2 xy, float2 ps, float2 pe, float width) {
				float2 pa = ps;
				float2 p = pe - ps;
				float2 pr = normalize(float2(-p.y, p.x)) * width;
				float2 pb = pe + pr;
				float2 pc = pe - pr;
				return in_triangle(xy, pa, pb, pc);
			}

			fixed4 frag (float4 sp:WPOS) : COLOR
			{
				// fixed2 red_green = sp.xy / _ScreenParams.xy;
				float2 xy = sp.xy / _ScreenParams.xy;
				float dist = distance(xy, float2(0.5, 0.5));

				//if (dist < _CenterRadius) {
				//	clip(-1);
				//	return fixed4(0,0,0,0);
				//}
				float2 points[] = {
					float2(0.5,1), float2(0,0.5), float2(0.5,0), float2(1,0.5),
					float2(1,1), float2(0,1), float2(0,0), float2(1,0),
				};
				float2 center   = float2(0.5,0.5);
				float width = _LineWidth * 0.5;

				if (in_triangle_line(xy, center, points[0], width)) { return fixed4(0,0,0,1); }
				if (in_triangle_line(xy, center, points[1], width)) { return fixed4(0,0,0,1); }
				if (in_triangle_line(xy, center, points[2], width)) { return fixed4(0,0,0,1); }
				if (in_triangle_line(xy, center, points[3], width)) { return fixed4(0,0,0,1); }

				if (in_triangle_line(xy, center, points[4], width)) { return fixed4(0,0,0,1); }
				if (in_triangle_line(xy, center, points[5], width)) { return fixed4(0,0,0,1); }
				if (in_triangle_line(xy, center, points[6], width)) { return fixed4(0,0,0,1); }
				if (in_triangle_line(xy, center, points[7], width)) { return fixed4(0,0,0,1); }

				clip(-1);
				return fixed4(0,0,0,0);

				// float red = dist;
				// float green = dist;
				// float blue  = 0.0;
				// float alpha = 1.0;
				// return fixed4(red, green, blue, alpha);
			}

			ENDCG
		}
	}
}